Probiotics have long been used in the nutrition of domestic animals. Different indications have been given for their use in the companion animals dogs and cats. Non-specific sensitivity (NSS), in dogs or cats, can occur in response to certain feed ingredients or in response to specific types of diets. It is characterized by soft fecal consistency. NSS is a recognised pathological condition in dogs and cats and can be defined as an intestinal disorder, characterized by the production of unformed wet feces, without further health impairment. The etiology of the condition is unclear, although the problem is related to dietary factors. It does not, however, seem to be limited to a specific ingredient. Loose fecal consistency can, for example, be reproduced by feeding commercial or home-cooked diets containing higher concentrations of animal derived protein sources. The problem may be associated with a reduction in colonic absorptive function, given that water, sodium and chloride absorption is lower and potassium secretion higher compared to that of unaffected individuals. Canned commercial diets are more problematical compared to dry kibble based pet food in NSS. A direct effect by dietary components on the gut wall or a disruption of the intestinal physiology with consequent impacts on absorptive intestinal function are potential causes of the disorder. Because little is known about the cause of NSS in dogs or cats, probiotics have not previously been thought useful to address this disorder.